As you know, he has for some years enjoyed access to various critical activities of the National Security Council, the Department of State, the Department of Defense, the Army, Navy and Air Force, the Research and Development Board, the Atomic Energy Commission, the Central Intelligence Agency, the National Security Resources Board, and the National Sciences Foundation. His access covers most new weapons being developed by the Armed Forces, war plans at least in comprehensive outline, complete details as to atomic and hydrogen weapons and stockpile data, the evidence on which some of the principal CIA Intelligence estimates is based, United States participation in the United Nations and NATO and many other areas of high security sensitivity.

Because the scope of his access may well be unique, because he has had custody of an immense collection of classified papers covering military, intelligence, and diplomatic as well as atomic energy matters, and because he also possesses a scientific background enabling him to grasp the significance of classified data of a technical nature, it seems reasonable to estimate that he is and for some years has been in a position to compromise more vital and detailed information affecting the national defense and security than any other individual in he United States.

While J. Robert Oppenheimer has not made major contributions to the advancement of science, he holds a respected professional standing among the second rank of American physicists. In terms of his mastery of Government affairs, his close liaison with ranking officials, and his ability to influence high level thinking, he surely stands in the first rank, not merely among scientists but among all those who have shaped postwar decisions in the military, atomic energy, intelligence, and diplomatic fields. As chairman or as an official on unofficial member of more than 35 important Government committees, panels, study groups, and projects, he has oriented or dominated key policies involving every principal United States security department and agency except the FBI.

The purpose of this letter is to state my own exhaustively considered opinion, based upon years of study, of the available classified evidence that more probably than not J. Robert Oppenheimer is an agent of the Soviet Union.

This opinion considers the following factors, among others.

1. The evidence indicating that as of April 1942: (a) He was contributing substantial monthly sums to the Communist Party; (b) His ties with communism had survive the Nazi-Soviet Pact and the Soviet attack upon Finland; (c) His wife and younger brother were Communists; (d) He had no close friends except Communists; (e) He had at least one Communist mistress; (f) He belonged only to Communist organizations, apart from professional affiliations; (g) The people whom he recruited into the early wartime Berkeley atom project were exclusively Communists; (h) He had been instrumental in securing recruits for the Communist Party, and (i) He was in frequent contact with Soviet Espionage agents.

2. The evidence indicating that: (a) In May 1942, he either stopped contributing funds to the Communist Party or else made his contributions though a new channel not yet discovered; (b) In April 1943 his name was formally submitted for security clearance; (c) He himself was aware at the time that his name had been so submitted and (d) He thereafter repeatedly gave false information to General Groves, Manhattan District, and the FBI concerning the 1939-April 1942 period.

3. The evidence indicating that: (a) He was responsible for employing a number of Communists, some of them not technical, at wartime Los Alamos; (b) He selected one such individual to write the official Los Alamos history; (c) He was a vigorous supporter of the H-bomb program until August 6, 1945, (Hiroshima), on which day he personally urged each senior individual working in this field to desist; and (d) He was an enthusiastic sponsor of the A-bomb program until the war ended, when he immediately and outspokenly advocated the Los Alamos Laboratory be disbanded.

4. The evidence indicating that: (a) He was remarkably instrumental in influencing the military authorities and the Atomic Energy Commission essentially to suspend H-bomb development from mid-1946 through January 31, 1950. (b) He has worked tirelessly, from January 31, 1950, onward to retard the United States H-bomb program; (c) He has used his potent influence against every postwar effort to expand capacity for producing A-bomb material; (d) He has used his potent influence against every postwar effort directed at obtaining larger supplies of uranium raw material; and (e) He has used his potent influence against every major postwar effort toward atomic power development, including the nuclear-powered submarine and aircraft programs as well as industrial power projects.

From such evidence, considered in detail, the following conclusions are justified: 1. Between 1939 and mid-1942, more probably than not, J. Robert Oppenheimer was sufficiently hardened Communist that he either volunteered espionage information to the Soviets or complied with a request for such information. (This includes the possibility that when he singled out the weapons aspect of atomic development as his personal specialty, he was acting under Soviet instructions.) 2. More probably than not, he has since been functioning as an espionage agent; and 3. More probably than not, he has since acted under a Soviet directive in influencing United States military, atomic energy, intelligence, and diplomatic policy.

It is to be noted that these conclusions correlate with information furnished by Klaus Fuchs, indicating the Soviets had acquired an agent in Berkeley who informed them about electromagnetic separation research during 1942 or earlier.

Needless to say, I appreciate the probabilities identifiable from existing evidence might, with review of future acquired evidence, be reduced to possibilities or they might also be increased to certainties. The central problem is not whether J. Robert Oppenheimer was ever a Communist; for the existing evidence makes abundantly clear that he was. Even an Atomic Energy Commission analysis prepared in early 1947 reflects this conclusion, although some of the most significant derogatory data had yet to become available. The central problem is assessing the degree of likelihood that he in fact did what a Communist in his circumstances at Berkeley, would logically have done during the crucial 1939-1942 period—that is, whether he became an actual espionage and policy instrument of the Soviets. Thus, as to this central problem, my opinion is that, more probably than not, the worst is in fact truth.

I am profoundly aware of the grave nature of these comments. The matter is detestable to me. Having lived with the Oppenheimer case for years, having studied and restudied all data concerning him that your agency made available to the Atomic Energy Commission through May 1953, having endeavored to factor in a mass of additional data assembled from numerous other sources, and looking back upon the case from a perspective in private life, I feel a duty simply to state to the responsible head of the security agency most concerned the conclusions which I have painfully crystallized and which I believe any fair-minded man thoroughly familiar with the evidence must also be driven to accept.

The writing of this letter, to me a solemn step, is exclusively on my own personal initiative and responsibility.